Amplifier thermal management

ABSTRACT

A thermally regulated amplifier system includes an amplifier unit, a temperature-sensing unit and a controller. The amplifier unit includes a power amplifier that has an adjustable gain function. The controller receives temperature readings from the temperature-sensing unit, computes the gain G(n) of the amplifier unit, and provides the computed gain of the amplifier G(n) to the power amplifier unit.

1. CLAIM OF PRIORITY

This patent application claims priority to European Patent Applicationserial number 06 008 798.8 filed on Apr. 27, 2006.

2. FIELD OF THE INVENTION

This invention relates to thermal management of an amplifier.

3. RELATED ART

Audio amplifiers typically automatically shutdown when the amplifiertemperature becomes too high. When used for entertainment, thisinterrupts the audio presentation. To circumvent this, disc jockeys mayhave several power amplifiers so they can switch to a second amplifierwhen the first amplifier becomes too hot. However, this entailsadditional capital cost, larger storage space and increases thetransportation burden.

U.S. Pat. No. 5,533,132 shows the use of acoustic air movement in aloudspeaker system to dissipate heat in the system. U.S. Pat. No.6,336,080 discloses thermal management of computers that uses a table ofdesired states. However, both prior art patents fail to disclose acomprehensive technique of thermal management of an amplifier system.

Therefore, there is a need for an improved amplifier thermal managementtechnique.

SUMMARY OF THE INVENTION

A thermally regulated amplifier system includes an amplifier unit, atemperature-sensing unit and a controller. The amplifier unit comprisesa power amplifier unit with an adjustable gain that is regulated by thecontroller. The controller may include a data processor andcommunication ports for communication between the controller and thetemperature-sensing unit and between the controller and the poweramplifier unit.

Advantageously, the temperature of the amplifier is fedback to controlthe applied amplifier power level. In case of an over temperature theamplifier system stills deliver a signal, although at a lower level thandesired. If used by a disc jockey, he can react to that by choosingmusic that requires a lower power level until the amplifier systemtemperature reaches an appropriate level.

Other systems, methods, features and advantages of the invention willbe, or will become, apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description, be within the scope ofthe invention, and be protected by the following claims.

DESCRIPTION OF THE DRAWINGS

The present invention can be better understood with reference to thefollowing drawings and description. The components in the figures arenot necessarily to scale, emphasis instead being placed uponillustrating the principals of the invention. Moreover, in the figures,like reference numerous designate corresponding parts throughout thedifferent views.

FIG. 1 is a block diagram illustration of a thermally regulated audioamplifier system;

FIG. 2 is a flow chart outlining operation of an amplifier thermalmanagement unit;

FIG. 3 illustrates a flow chart outlining operation of a furtheramplifier thermal management unit;

FIG. 4 illustrates a flow chart outlining operation of an amplifiergain-regulation unit used in the amplifier thermal management unit ofFIGS. 2 and 3;

FIG. 5 illustrates a flow chart outlining operation of a fan controlunit of the amplifier thermal management unit of FIG. 3;

FIG. 6 illustrates a table of power output values of the amplifier unitillustrated in FIG. 1;

FIG. 7 illustrates a temperature graph of an unregulated amplifiersystem of the prior art;

FIG. 8 illustrates a temperature graph of the regulated amplifier systemof FIG. 1;

FIG. 9 illustrates a DI-gain and an I-gain graph of the regulatedamplifier system of FIG. 1;

FIG. 10 illustrates a regulation gain graph of the regulated amplifiersystem of FIG. 1;

FIG. 11 illustrates an expanded view of section A illustrated in FIG. 10of the regulation gain response of the regulated amplifier of FIG. 1;

FIG. 12 illustrates a temperature graph of a further regulated amplifiersystem as that has fan control;

FIG. 13 illustrates an I-gain and a DI-gain graph of the furtherregulated amplifier system;

FIG. 14 illustrates a regulation gain graph of the further regulatedamplifier system;

FIG. 15 illustrates a fan status graph of the further regulatedamplifier system;

FIG. 16 illustrates a temperature graph of still a further regulatedamplifier system, which comprises a large mass heat sink;

FIG. 17 illustrates a temperature graph of still a further regulatedamplifier system, which comprises a good thermal heat sink;

FIG. 18 illustrates a temperature graph of still a further regulatedamplifier system, which comprises a fan control; and

FIG. 19 illustrates a temperature graph of still a further regulatedamplifier system, which comprises a poor thermal heat sink.

DETAILED DESCRIPTION

The present invention provides feedback of the temperature of theamplifier system for control of the applied amplifier power level, wherethe thermally regulated amplifier system may include an amplifier unit,a temperature-sensing unit and a controller. The amplifier unit includesa power amplifier unit with an adjustable gain that is regulated by thecontroller. The controller may include a data processor andcommunication ports connected by a communication channel between thecontroller and the temperature-sensing unit and between the controllerand the power amplifier unit.

The temperature sensing unit may sample the amplifier system temperatureT(n) at fixed intervals and transmits the sampled amplifier systemtemperature T(n) reading to the controller. The data processor of thecontroller determines a gain G(n) of the power amplifier unit and setsthe gain G(n) of the power amplifier unit to the gain G(n) of the poweramplifier via the communication port that is between the controller andthe power amplifier unit.

The thermally regulated amplifier system may also include a fan thatoperates when the amplifier system temperature T(n) exceeds a fantrigger temperature and stops operating when the amplifier systemtemperature T(n) is below the fan trigger temperature. Of coursehystersis may be added to the thresholds as necessary.

For example, a technique for regulating an amplifier system temperatureincludes receiving a volume level setting V(n) from a user. Then anamplifier system temperature T(n) value is read by a temperature sensingunit at regular intervals. Following this, the amplifier systemtemperature T(n) is compared against a gain regulation temperatureT_(reg) _(—) _(on). If the amplifier system temperature T(n) is belowthe gain regulation temperature T_(reg) _(—) _(on), then the gain G(n)of the power amplifier unit is adjusted to the gain level determined bythe volume setting V(n). When the amplifier system temperature T(n) isabove the gain regulation temperature T_(reg) _(—) _(on), the gain G(n)of the power amplifier unit is adjusted to a gain less than the gainlevel set by the volume setting V(n).

Further, operation of a fan for additional cooling may be provided ifnecessary, where it may be verified whether the amplifier systemtemperature T(n) is above a fan trigger temperature T_(fan) _(—) _(on).When the amplifier system temperature T(n) is above the fan triggertemperature T_(fan) _(—) _(on) then a fan is activated. The fan may beturned off when the amplifier system temperature T(n) is below the fantrigger temperature T_(fan) _(—) _(on).

Historical (e.g., stored) values of the amplifier system temperatureT(n) may be used to choose the gain G(n) of a power amplifier unit whenthe amplifier system temperature T(n) is above the gain regulationtemperature T_(reg) _(—) _(on).

A rate of change of the amplifier system temperature T(n) may be used toestablish the gain G(n) of the power amplifier unit. A rapid change ofthe amplifier system temperature T(n) will suggest a large change in thegain G(n) of the power amplifier unit.

The two most recent amplifier system temperature T(n) readings may beused to compute the rate of change of the amplifier system temperatureT(n). The use of the two most recent amplifier system temperature T(n)readings provide for a relatively easy computation of the rate of changeof the amplifier system temperature T(n).

More than the two most recent amplifier system temperature T(n) readingmay be used to compute the rate of change of the amplifier systemtemperature T(n). The use of larger number of temperature data pointsaids in preventing spurious amplifier system temperature data pointsfrom making abrupt change to the computed change of the amplifier systemtemperature T(n).

The historical gain G(n) of the power amplifier unit may also be used tocompute the gain G(n) of the power amplifier unit. The use of thehistorical gain G(n) offers another source of information for theassessment of the gain G(n), in addition to or as an alternative to thehistorical data of the amplifier system temperature T(n).

In time-discrete operated systems, reading the values of the amplifiersystem temperature T(n) at regular intervals may facilitate theselection of the gain G(n) of a power amplifier.

The gain G(n) of the power amplifier unit may be computed in decibelunits by the following equation:

$\begin{matrix}{{G(n)} = {{G\left( {n - 1} \right)} - {c_{d}\left\lbrack {{k_{n}{T(n)}} - {\sum\limits_{x = 1}^{x = a}{k_{n - x}{T\left( {n - x} \right)}}}} \right\rbrack}}} & (1)\end{matrix}$

-   -   where,        -   c_(d) comprises a constant value,        -   k_(n) is a coefficient,        -   a, n comprises a integer value, and        -   2≦a,        -   k_(n−x)            k_(n−(x+1)) for 1≦x≦a, and

$k_{n} = {\sum\limits_{x = 1}^{x = a}k_{n - x}}$

The restriction that k_(n−x)

k_(n−(x+1)) for 1≦x≦a gives greater weight to the earlier amplifiersystem temperature T(n) and prevents a more recent temperature T(n)reading from causing sudden changes to the G(n).

The condition that

$k_{n} = {\sum\limits_{x = 1}^{x = a}k_{n - x}}$causes the term

$\left\lbrack {{k_{n}{T(n)}} - {\sum\limits_{x = 1}^{x = a}{k_{n - x}{T\left( {n - x} \right)}}}} \right\rbrack$of equation (1) to be zero when there is no rate of change of T(n). Thusthe gain of the power amplifier G(n) of equation (1) remains constantwhen the temperature T(n) remains constant.

Regulation of the gain G(n) commences when the amplifier systemtemperature T(n) exceeds the gain regulation temperature T_(reg) _(—)_(on). When the regulation of G(n) commences, the T(n) is on theincrease and this causes the term

$\left\lbrack {{k_{n}{T(n)}} - {\sum\limits_{x = 1}^{x = a}{k_{n - x}{T\left( {n - x} \right)}}}} \right\rbrack$of equation (1) to be of positive value and the gain variable G(n) ofequation (1) to be of a negative value. Hence the gain variable G(n)commences on a decreasing trend.

A negative number in decibel units will have a value between zero andone. When the gain G(n) of the power amplifier unit is adjusted to thecomputed gain G(n), the output of the power amplifier is reduced. Thisreduction in turn, deters the amplifier system temperature T(n) fromrising.

The gain G(n) of the power amplifier may also be computed by theequations below where the gain G(n) is in units of decibel.

$\begin{matrix}{{G_{1}(n)} = {{G_{1}\left( {n - 1} \right)} - {c_{d}\left\lbrack {{k_{n}{T(n)}} - {\sum\limits_{x = 1}^{x = a}{k_{n - x}{T\left( {n - x} \right)}}}} \right\rbrack}}} & (2)\end{matrix}$where, C_(d) comprises a constant value, k_(n) is a coefficient, and a,n comprises a integer value, and 2≦a,

$\begin{matrix}{{{k_{n - x} \prec {k_{n - {({x + 1})}}\mspace{14mu}{for}\mspace{14mu} 1} \leq x \leq a},{{{and}\mspace{14mu} k_{n}} = {\sum\limits_{x = 1}^{x = a}k_{n - x}}}}{{G_{2}(n)} = {{G_{2}\left( {n - 1} \right)} + {c_{i}\left\lbrack {T_{m} - {T(n)}} \right\rbrack}}}} & (3)\end{matrix}$where, c_(i) comprises a constant value, and T_(m) is the uppertemperature control limit of the amplifier system temperature readingT(n).G(n)=G ₁(n)+G ₂(n)  (4)Equations (1) and (2) are similar. From earlier comments on equation(1), one can see that the variable G₁(n) starts with a decreasing rate.

The equation (3) shows a gain variable G₂(n) that increases when theamplifier system temperature T(n) reading is below the upper temperaturecontrol limit T_(m). When the regulation of the gain of G(n) commences,T(n) exceeds the gain regulation temperature T_(reg) _(—) _(on).Moreover, T(n) has a value that is below T_(m). In view of this, theequation (3) shows that the gain variable G₂(n) commences with apositive value and is on an increasing trend. The gain variable G₂(n)can be viewed as the gain component, which acts to increase and restoreG(n) back to a level that produces the desired volume level.

The values of the variables G₁(n) and G₂(n) may be set to zero decibelwhen −G₁(n)<G₂(n). It may be the case that when the gain regulation ofthe power amplifier commences, the gain variable G₁(n) has negativevalues and the gain variable G₂(n) have positive values. This steprestricts the computed gain G(n) of the power amplifier unit to havingnegative values or a value of zero. The computed gain G(n) of the poweramplifier unit are preferably in units of decibel and will thus have anabsolute value between zero and one. When the controller adjusts thegain of the power amplifier unit to the computed gain G(n), the outputof the power amplifier unit will be reduced.

FIG. 1 shows a schematic block diagram of a thermally regulated audioamplifier system 8. The system 8 includes an amplifier thermalmanagement unit 9 that comprises a temperature polling unit 1 and anamplifier gain-regulation unit 2. The output of the temperature-pollingunit 1 is supplied to the amplifier gain-regulation unit 9, whichsupplies a signal on a line 102 to a power amplifier unit 6 within anamplifier unit 10. The amplifier unit 10 includes a volume control unit3 and an audio pre-amplifier unit 5. The audio pre-amplifier unit 5receives a signal from the volume control unit 3 and a signal from anaudio signal source 4, and outputs a signal to the power amplifier unit6. The power amplifier unit 6 in turn drives a loudspeaker unit 7.

In the present example, the temperature-polling unit 1 includes at leastone temperature sensor (not shown) and senses the temperature of theaudio amplifier system 8 at regular time intervals but also may, forexample, continuously measure the temperature. The polled temperaturereading is supplied to the amplifier gain-regulation unit 2 thatcomputes the regulation-gain of the power amplifier unit 6. The volumecontrol unit 3 receives a volume level setting from a user. The volumelevel setting is supplied to the audio pre-amplifier unit 5 whichreceives the audio signal from the audio signal source 4 and amplifiesthe audio signal by a factor corresponding to the volume level setting.The amplified audio signal is provided to the power amplifier unit 6whose output power corresponds, accordingly, to the volume level settingas well as to the regulation-gain computed by the amplifiergain-regulation unit 2. When the power amplifier is unregulated, thegain of the power amplifier unit 6 may be set to one.

FIG. 2 illustrates a flow chart 23 outlining the operation of theamplifier thermal management unit 9. The flow chart 23 starts with thepolling of an amplifier system temperature T(n) in regular timeintervals in step 10. The polled amplifier system temperature T(n)reading is then compared against a regulation-start temperature T_(reg)_(—) _(on) in step 11. If T(n) is greater than T_(reg) _(—) _(on),amplifier gain-regulation then step 12 is then executed. If T(n) is notgreater than T_(reg) _(—) _(on), the procedure again starts with step10. Following step 12 the operation returns to step 10.

In the present example, the amplifier system temperature T(n) is polledevery 20 seconds with a one degree Celsius (° C.) resolution. Theamplifier gain-regulation unit 12 is activated when the amplifier systemtemperature T(n) exceeds the regulation start temperature T_(reg) _(—)_(on), which is set at 70° C. The regulation may, e.g., take place intwo different manners. One way is to reduce the gain by or to oneconstant value when the regulation start temperature T_(reg) _(—) _(on)is exceeded. The other way is that the gain is reduced by or to a firstconstant value, and when the temperature still exceeds the regulationstart temperature T_(reg) _(—) _(on), it is reduced by or to a secondvalue and so on.

FIG. 3 illustrates a flow chart 24 outlining an alternative controlroutine. The flow chart 24 has steps similar to those shown in FIG. 2where the difference between FIGS. 2 and 3 is the inclusion of a fancontrol step after the polling of the amplifier system temperature T(n)in step 10. The flow chart 24 again starts with the polling of anamplifier system temperature T(n) in step 10. A fan is activated in step13 when a certain fan control temperature is exceeded by the temperatureamplifier system temperature T(n). The fan control temperature may behigher or lower than the regulation-start temperature T_(reg) _(—)_(on). Following this, the amplifier system temperature T(n) is comparedagainst a regulation-start temperature T_(reg) _(—) _(on) in thedecision step 11.

FIG. 4 illustrates a flow chart of the operation of an amplifiergain-regulation unit used for amplifier thermal management (see step 12)as outlined in FIGS. 2 and 3. The amplifier gain-regulation routine 12starts with the computation of a DI-gain D_(gain)(n) of the poweramplifier (D=Differential, I=Integral), in step 14. D_(gain)(n) may becomputed with the equation below. The computed D_(gain)(n) are in unitsof decibel.D(n)=0.4T(n)−0.05T(n−1)−0.1T(n−2)−0.25T(n−3)  (5)where, T(n) is a polled amplifier system temperature, and n is aninteger and denotes the sequence number of the polled amplifier systemtemperature and has a value greater than 0.D _(gain)(n)=D _(gain)(n−1)−c _(d) D(n)  (6)where, ci is a constant c_(d) and may have a value of, for example,0.85.

The computation of I-gain I_(gain)(n) of the amplifier is performed instep 15, for example, with the equations below. The computed I_(gain)(n)are in units of decibel.I(n)=I(n−1)+[T _(max) −T(n)]  (7)where, T_(max) is a regulation-maximum temperature and may have a valueof, for example, 81° C.I _(gain)(n)=c _(i) I(n)  (8)where, ci is a constant and may have a value of, for example, 0.05.

After step 15, the negative value of the D-gain D_(gain)(n) is comparedagainst the value of the I-gain I_(gain)(n) in decision step 16. If thenegative value of the D_(gain)(n) is less than the value of I_(gain)(n)then the values of D_(gain)(n), I_(gain)(n) and variable I(n) will beset to zero decibel in step 17. After this, the regulation-gainR_(gain)(n) of the amplifier is determined in step 18. R_(gain)(n) isthe sum of D_(gain)(n) and I_(gain)(n).

If the negative value of D_(gain)(n) is not less than the value ofI_(gain)(n), then the next step is computation of R_(gain)(n) in step18. The next step 19 involves setting the gain of the power amplifier tothe value of R_(gain)(n).

Referring to equation (1), the computation of the variable D(n) is ameasure of the rate of change of the amplifier system temperaturereading T(n). The greater the rate of change of T(n), the greater thevalue D(n).

The value of D(n) is derived from the current system reading T(n) andthe previous three weighted amplifier system temperature readings ofT(n−1), T(n−2), and T(n−3). The earlier system reading is given greaterweight than the later amplifier system temperature reading. This is toavoid generating steep changes to the DI-gain D_(gain)(n).

The DI-gain D_(gain)(n) as shown in equation (2), comprises of the sumof the previous DI-gain D_(gain)(n−1) and the product of the negativevalue of the constant c_(d) and of the variable D(n). When the rate ofchange of the amplifier system temperature reading T(n) is positive, thevariable D(n) generated will be a positive number and the value ofD_(gain)(n) will decrease. Conversely, when the rate of change of T(n)is negative, the value of the variable D(n) derived will be a negativenumber and the value of D_(gain)(n) will increase. If the temperaturereading T(n) does not change over time, the value of the variable D(n)achieved is zero and the value of D_(gain)(n) will stay unchanged.

FIGS. 2 and 3 show that the amplifier gain-regulation unit 12 is notoperating when the amplifier system temperature T(n) has a value lessthan the regulation-start temperature T_(reg) _(—) _(on) When thetemperature T(n) increases in value and exceeds T_(reg) _(—) _(on), theamplifier gain-regulation unit 12 will start to operate. Hence, when theamplifier gain-regulation unit 12 starts operating, the D_(gain)(n) willstart with a negative value as the variable D(n) has a positive valuewhile the previous D_(gain)(n−1) has a zero value. Moreover, the valueof the D_(gain)(n) is on a decreasing trend in the beginning since T(n)is on a increasing trend.

The value of the variable I(n) in equation (3) is a sum of the previousvalue of variable I(n−1) and the value of [T_(max)−T(n)]. The constantT_(max) is the regulation-maximum temperature, which has for example avalue of 81° C. In equation (4), the value of the I-gain I_(gain)(n)comprises of the product of the constant c_(i) and the variable I(n).The value of the constant c_(i) is for example 0.05.

At the initial phase when the amplifier regulation unit starts tooperate, the value of the amplifier system temperature T(n) will exceedthe regulation start temperature T_(reg) _(—) _(on) and will have avalue that is between the value of T_(reg) _(—) _(on) and the value ofregulation-maximum temperature T_(max). The I-gain I_(gain)(n) thusstarts with a positive value since the value of [T_(max)−T(n)] is apositive number and I_(gain)(n−1) has a zero value. Furthermore,I_(gain)(n) starts on an increasing trend as the value of [T_(max)−T(n)]is positive.

If the value of the amplifier system temperature T(n) reaches theregulation-maximum temperature T_(max), then [T_(max)−T(n)] attains azero value. If the temperature T(n) stays at T_(max) then the value ofI_(gain)(n) will also stay unchanged.

The value of the DI-gain D_(gain)(n) is dependent on the constant c_(d),which for example has a value of 0.85. The value of the I-gainI_(gain)(n) is dependent on the constant c_(i), which has for example avalue of 0.05. The small value of the constant c_(i) relative to thevalue of the constant c_(d) tends to keep the absolute value ofD_(gain)(n) more than the absolute value of I_(gain)(n).

Referring still to FIG. 4, the value of the negative value of theDI-gain D_(gain)(n) is compared with the I-gain I_(gain)(n) in step 16.If the negative value of D_(gain)(n) is less than the value ofI_(gain)(n), then the value of the D_(gain)(n), the value of I_(gain)(n)and the value of the variable I(n) are set to zero decibel in step 17.Hence the decision step 16 keeps the negative value of D_(gain)(n) notless than the value of I_(gain)(n) when the process flow reaches step18.

The regulation gain R_(gain)(n) is computed in step 18 and is the sum ofthe DI-gain D_(gain)(n) and the I-gain I_(gain)(n). The processing ofstep 16 thus ensures that the value of R_(gain)(n) is either zero orless than zero. The gain of the power amplifier is set to the value ofR_(gain)(n) in step 19. A number of zero or less than zero in decibelunits will have a value of either one or less than one.

Thus the amplifier regulation unit starts to operate when the amplifiersystem temperature T(n) exceeds the regulation-start temperature T_(reg)_(—) _(on). A rising amplifier system temperature T(n) will generate alower gain for the power amplifier unit. In this manner thermalregulation of the amplifier system is achieved.

FIG. 5 illustrates a flow chart of the fan control logic 13 of theamplifier thermal management unit of FIG. 3. The fan control logic 13starts with the comparison of the amplifier system temperature T(n) witha fan-start temperature T_(fan) _(—) _(on) in step 20. If T(n) isgreater than T_(fan) _(—) _(on), the fan is switched on in step 22. IfT(n) is not greater than T_(fan) _(—) _(on), then the fan is switchedoff in step 21. The fan is operating when T(n) exceeds T_(fan) _(—)_(on.)

FIG. 6 shows a table of output values, as an example, of the poweramplifier unit 6 of the amplifier system of FIG. 1. For the first 2000seconds, the amplifier is caused to produce 25 watts of power. Theamplifier then outputs 8 watts for the next 1000 seconds. Thereafter,the amplifier gives out 0.8 watts for 4000 seconds. After this, theamplifier outputs 24 watts for 2000 seconds. Lastly, the amplifiergenerates 16 watts for 1000 seconds. The power values, times andthreshold values are cited by way of example. One of ordinary skill inthe art will recognize that these values of course change as part of thespecific implementation details of a system incorporating the inventiveclose loop temperature control to provide a thermally regulatedamplifier system.

The table of amplifier output values is used in the following figuresmerely as example. These power output values examples are for anamplifier in an unregulated state. When the amplifier is in a regulatedstate, the power output values as stated in the table are multipliedwith a gain factor that is determined by the amplifier gain-regulationunit.

FIG. 7 illustrates a temperature graph 25 of an unregulated amplifiersystem of the prior art. The unregulated amplifier system produces apower output value as shown in FIG. 6. The amplifier system temperatureT(n) starts from an initial temperature of about 50° C. and rises to apeak temperature of about 128° C. after 2000 seconds. Then the amplifiersystem temperature T(n) decreases to about 104° C. at the 3000 secondtime point and then falls further to about 62° C. at the 7000 secondtime point before rising to about 120° C. at the 9000 second time point.Finally, the amplifier system temperature T(n) declines to about 114° C.at the 10,000 second time point.

During the operation of the prior art unregulated amplifier system, theamplifier system temperature T(n) reading fluctuates between a high ofabout 128° C. and a low of about 62° C. The amplifier system has athermal resistance R_(th) of 0.9° C. per watt, and a thermal capacitanceC_(th) of 855 joules per degree Celsius.

The graphs in FIGS. 8-11 plot different parameters of a regulatedamplifier system 8. The regulated amplifier system 8 has the samethermal features as the unregulated amplifier system that generated thetemperature versus time curve 38 in FIG. 7. The regulated amplifiersystem 8 has a thermal resistance R_(th) of 0.9° C. per watt and athermal capacitance C_(th) of 855 joule per degrees Celsius. The thermalmanagement unit 9 of the regulated amplifier system 8 has aregulation-start temperature T_(reg) _(—) _(on) of 70° C. and aregulation-maximum temperature T_(max) of 81° C. When the amplifiersystem temperature T(n) is above T_(reg) _(—) _(on), the regulatedamplifier system 8 produces the power output value as shown in FIG. 6.The regulated amplifier system 8 produces the power output value asshown in FIG. 6 multiplied by a regulation gain factor when temperatureT(n) is below T_(reg) _(—) _(on). The amplifier gain-regulation unit 2determines the regulation gain factor.

FIG. 8 illustrates a temperature graph 26 of the regulated amplifiersystem 8 of FIG. 1. The amplifier system temperature T(n) on line 39starts with a temperature reading of about 50° C. at 0 second timepoint. The temperature T(n) then rises to about 70° C. at 300 secondtime point and continues to rise to about 81° C. at 840 second timepoint. From this time point onwards, the temperature T(n) readingremains roughly flat until about 2000 second time point. Then thetemperature T(n) reading begins to decline to about 77° C. at 2300second time point. After this time point, the temperature T(n) readingincreases to about 80° C. at 3000 second time point. From the 3000second time point onwards, the temperature T(n) readings falls to about60° C. at 7000 second time point.

The amplifier system temperature T(n) starts to increase at the 7000second time point to about 81° C. at 8000 second time point. From thistime point onwards the temperature T(n) reading stays relativelyconstant until 9000 second time point. After the 9000 second time point,the temperature T(n) reading decreases slightly by about 1° C. at 9100second time point and then increases around 1° C. at 10,000 second timepoint.

The amplifier gain-regulation unit 2 keeps the amplifier systemtemperature T(n) to a maximum reading of about 81° C. as an example inaccordance to an aspect of the invention. In comparison, the temperaturegraph of an unregulated amplifier system in FIG. 7 under similarenvironment has a high temperature of about 128° C. The amplifier systemtemperature T(n) on the line 39 in FIG. 8 of the regulated amplifierdoes not show an overshoot over the temperature maximum limit of 81° C.There is no amplifier regulation when T(n) is below the regulation-starttemperature T_(reg) _(—) _(on) of 70° C. When T(n) exceeds T_(reg) _(—)_(on), the amplifier gain-regulation unit 2 starts operating and theoutput of the power amplifier unit 6 is regulated.

FIG. 9 illustrates a DI-gain and an I-gain graph 27 of the regulatedamplifier system 8 of FIG. 1. The I-gain I_(gain)(n) graph lines 42 and42′ have positive values while the DI-gain D_(gain)(n) graph lines 40and 40′ contain negative values.

The DI-gain D_(gain)(n) line 42 starts from a value of about 0 decibel(dB) at 300 second time point and falls to about −11.9 dB value at 840second time point. The D_(gain)(n) line 42 then remains mostly flataround the −11.9 dB value until 2000 second time point. At the 2000second time point, the D_(gain)(n) line 42 starts to increase from avalue of about −11.9 dB to a value of about −8.7 dB at about 2300 secondtime point before falling to about −12.0 dB at 3000 second time point.Then the D_(gain)(n) line 42 rises sharply to a value of about 0 dB at3100 second time point.

At 7100 second time point, the D_(gain)(n) line 42′ starts from a valueof about 0 dB and decreases to a value of about −11.0 dB at 8000 secondtime point. Line 42′ stays mostly flat around the −11.0 dB value fromthe 8000 second time point to 9000 second time point. From the 9000second time point, the D_(gain)(n) line 42′ begins to rise to a value ofabout −9.9 dB at 9100 second time point. Then the D_(gain)(n) line 42′declines from a value of about −9.9 dB at the 9100 second time point toa value of about −11.0 dB at 10000 second time point D_(gain)(n) graphlines 42 and 42′ behave in agreement with the FIG. 4 description of theD_(gain)(n). The D_(gain)(n) lines 42 and 42′ exhibit a positive slopefrom the 2000 second time point to the 2300 second time point and fromthe 9000 second time point to the 9100 second time point. When theD_(gain)(n) has a positive slope, the corresponding amplifier systemtemperature T(n) line 39 in FIG. 8 has a negative slope.

Lines 42 and 42′ are mostly constant from the 840 second time point tothe 2000 second time point and from the 8000 second time point to the9000 second time point. When D_(gain)(n) is flat, the correspondingamplifier system temperature T(n) line 39 as shown in FIG. 8 alsoexhibits a constant reading.

From the 300 second time point to the 840 second time point and from the2300 second time point to the 3000 second time point, line 42 shows anegative slope. Line 42′ displays a negative slope from the 7100 secondtime point to the 8000 second time point and from the 9100 second timepoint to the 10000 second time point. When the DI-gain D_(gain)(n) lines42 and 42′ show a negative slope, the corresponding amplifier systemtemperature T(n) in FIG. 8 shows a positive amplifier system temperatureslope.

The I-gain I_(gain)(n) line 40 begins with a value of 0 dB at about 300second time point and then rises to a value of about 4.4 dB at 840 sectime point. From this time point onwards, the I_(gain)(n) line 40remains flat until about 2000 second time point. At the 2000 second timepoint, the I_(gain)(n) line 40 begins to rise and reaches about 10 dB at3000 second time point. The I_(gain)(n) line 40 rises slightly by about0.1 dB and then drops sharply to 0 dB at 3100 second time point.

The I_(gain)(n) line 40′ starts at 7100 second time point with a valueof about 0 dB and rises to about 5.5 dB at 8000 second time point. Line40′ is constant at about 5.5 dB from the 8000 second time point to 9000second time point. At the 9000 second time point, the line 40′ starts torise from a value of about 5.5 dB to a value of about 7.3 dB at the10,000 second time point.

The behavior of I_(gain)(n) graph lines 40 and 40′ are in accordancewith the FIG. 4 description of I_(gain)(n). The amplifier systemtemperature T(n) exceeds 70° C. at about the 300 second time point andaround the 7100 second time point. I_(gain)(n) graph lines 40 and 40′commence at the time points where the amplifier system temperature T(n)exceeds 70° C.

Line 40 of the I_(gain)(n) rises from the 300 second time point to the840 second time points and from the 2000 second time point to the 3000second time point. The I_(gain)(n) line 40′ rises from the 7100 secondtime point to the 8000 second time point and from the 9000 second timepoint to the 10,000 second time point. Lines 40 and 40′ increase whenthe amplifier system temperature T(n) is below the regulation-maximumtemperature T_(max) of 81° C.

From the 840 second time point to the 2000 second time point and fromthe 8000 second time point to the 9000 second time point, theI_(gain)(n) lines 40 and 40′ are almost flat. The I_(gain)(n) lines 40and 40′ are mostly constant when the amplifier system temperature T(n)has the same value as the regulation-start temperature T_(reg) _(—)_(on) of 81° C.

FIG. 10 illustrates a regulation gain graph 28 of the regulatedamplifier system 8 of FIG. 1. The regulation-gain R_(gain)(n) line 44 ofthe amplifier system starts at 0 dB at about 300 second time point andfalls to about −7.5 dB at 840 second time point and then stays around−7.5 dB value until the 2000 second time point. From the 2000 secondtime point, the R_(gain)(n) line 44 starts to rise to roughly −2.0 dB at3000 second time point. At the 3000 second time point, the R_(gain)(n)line 44 rises sharply to 0 dB at about 3100 second time point.

R_(gain)(n) line 44′ begins with a value of 0 dB at 7100 second timepoint and decreases to a value of about −5.5 dB at 8000 second timepoint. The R_(gain)(n) line 44′ then remains around a −5.5 dB valueuntil 9000 second time point. From the 9000 second time point, the line44′ rises to about −3.5 dB at 9400 second time point. After that, theR_(gain)(n) line 44′ falls to about −4.0 dB at 9500 second time point.The R_(gain)(n) line 44′ then rises to about −3.7 dB at 10000 secondtime point.

Lines 44 and 44′ illustrate the thermal regulation of the amplifiersystem 8 via the gain regulation of the power amplifier unit 6. Theregulation-gain R_(gain) is activated at the point when the amplifiersystem temperature T(n) exceeds the regulation-start temperature T_(reg)_(—) _(on) of 70° C. at the 300 second time point and at the 7100 secondtime point. The value of the R_(gain)(n) starts to reduce at the 300second time point and at the 7100 second time point when the amplifiersystem temperature T(n) is increasing. In similar manner, the value ofR_(gain)(n) also increases when T(n) starts to decrease in value at the2000 second time point and 9000 second time point.

FIG. 11 illustrates an expanded view of a section A of the regulationgain response of the regulated amplifier system 8 of FIG. 1. The timeframe of the expanded view is from 760 second time point to 2040 secondtime point. Gain line 44 versus time starts from a value of about −6.9dB at the 760 second time point and falls to a value of about −7.26 dbat 770 second time point. The R_(gain)(n) line 44 then rises from avalue of about −7.26 dB at the 770 second time point to a value of about−7.03 db at 1000 second time point. From the 1000 second time point tothe 1300 second time point, the R_(gain)(n) line 44 fluctuates betweenabout −7.03 db and about −7.65 db. And from the 1300 second time pointto the 2000 second time point, the R_(gain)(n) line 44 varies betweenabout −7.0 dB and about −7.65 db.

The graphs in FIGS. 12-15 plot different parameters of an alternativeregulated amplifier system. The distinction between the alternativeregulated amplifier system and the regulated amplifier system is a fancontrol unit in the alternative regulated amplifier system. The fancontrol unit is activated with the system amplifier temperature T(n)exceeds a fan-start temperature T_(fan) _(—) _(on) of 68° C. The thermalresistance of the further amplifier system is of 0.4° C. per watt whenthe fan is activated and is of 0.9° C. per watt when the fan stopsturning.

FIG. 12 illustrates a temperature graph 30 of a regulated amplifiersystem that has fan control. Line 45 of temperature graph 30 begins witha temperature reading of about 50° C. at 0 second time point andincreases to around 81° C. at 2000 second time point. From around the81° C. at the 2000 second time point, the line 45 drops to approximately70° C. at the 3000 second time point. The line 45 decreases from about70° C. at the 3000 second time point to around 64° C. at the 3130 secondtime point and then gently decline further to around 62° C. at the 7000second time point.

At approximately 62° C. at the 7000 second time point, the temperaturegraph rises to about 79° C. at the 9000 second time point. Then the line45 falls from approximately 79° C. at the 9000 second time point toaround 73° C. at the 10,000 second time point.

The highest temperature reading on the line 45 is about 81° C., which isaround the maximum control temperature limit T_(max) of 81° C. Relativeto temperature graph 26 of FIG. 8 of the regulated amplifier system, thetemperature graph 30 has a slower rate increase from the 0 second timepoint to the 2000 seconds and from the 7000 second time point to the9000 second time point. This is due to the lower thermal resistance ofthe alternative embodiment amplifier unit when the fan is activated. Thefan is activated with the amplifier system temperature T(n) exceeds thefan-start temperature T_(fan) _(—) _(on) of for example 68° C. The line45 has a gentle decline from the 3130 second time point to the 7000second time point because the fan is not operating when the temperatureT(n) is below the value T_(fan) _(—) _(on).

FIG. 13 illustrates an I-gain and a DI-gain graph 31 of the furtherregulated amplifier system. The I-gain graph includes lines 46 and 46′,which have positive values. The DI-gain graph includes lines 48 and 48′,which have negative values. I-gain line 46 of graph 31 starts with avalue of 0 decibel (dB) at about 260 second time point and rises toabout 10.4 dB at the 2050 second time point before falling steeply to 0dB.

Beginning at the 7100 second time point, the I-gain line 46′ has a valueof 0 dB and ends with a value of 0 dB at 7870 second time point. TheI-gain line 46′ oscillates between a high value of about 4.0 dB and 0dB. DI-gain line 48 starts at with a value of about 0 dB at the 260second time point and decreases to about −11.6 dB before rising steeplyto approximately 0 dB at 2050 second time point. The DI-gain line 48′begins at the 7110 second time point with a value of about 0 dB andswings between around 0 dB and about −4.1 dB. The graph line 48′ stopsat approximately 0 dB at 7870 second time point.

The I-gain lines have positive values and the DI-gain lines havenegative values. The gain graphs starts when the amplifier systemtemperature exceed the regulation-start temperature T_(reg) _(—) _(on)of 70° C. The I-gain and DI-gain lines terminate at an earlier timepoint as compared with the same gain graph 27 of FIG. 9. This is due toa faster falling rate of the temperature line 45 of the alternativeamplifier system temperature T(n) when the fan is operating.

FIG. 14 illustrates a regulation gain graph 32 of the further regulatedamplifier system. Regulation-gain R_(gain)(n) line 50 of the graph 32starts at about the 300 second time point with a value of 0 dB and stopsat about the 2050 second time point with a value of 0 dB. Values on theline 50 vary between 0 dB and a low of about −2.4 dB.

From the 7100 second time point with a value of 0 dB, the R_(gain)(n)line 50′ of the graph 32 commences and ceases at about the 7870 secondtime point with a value of about 0 dB. Line 50′ fluctuates between 0 andabout −0.6 dB. The regulation-gain R_(gain)(n) lines 50 and 50′ beginwhen the amplifier system temperature T(n) exceeds the regulation-starttemperature T_(reg) _(—) _(on) of 70° C. and according to an aspect ofthe invention has negative dB values. Lines 50 and 50′ have smallervalues as compared to regulation-gain R_(gain)(n) lines 44 and 44′ ofgraph 28 of the regulated amplifier system. This is due to the lowerthermal resistance of the alternative embodiment amplifier system whenthe fan is activated.

FIG. 15 shows a fan status graph 33 of the alternative regulatedamplifier system. The fan is switched on from around the 310 second timepoint to about the 3040 second time point (see line 52) and from aroundthe 7060 second time point to approximately 10,000 second time point(see line 52'). The fan is operating when the amplifier systemtemperature T(n) exceeds fan-start temperature T_(fan) _(—) _(on) of 68°C. When the amplifier system temperature T(n) drops below the fan-starttemperature T_(fan) _(—) _(on) the fan is switched off.

FIGS. 16-19 illustrate the system operation under different conditions.The figures are temperature graphs generated by yet another thermallyregulated amplifier system according to an aspect of the invention thatincludes a different heat dissipation feature for each temperaturegraph. This regulated amplifier system generates the power with a poweroutput value that is shown in the table in FIG. 6 multiplied by anamplifier regulation gain R_(gain)(n). The amplifier regulation gainR_(gain)(n) is determined by the amplifier regulation unit 2.

FIG. 16 shows a temperature graph 34 of a regulated amplifier system,that includes a large mass heat sink. The distinction with the regulatedamplifier system and the regulated amplifier system that producedtemperature graph 26 of FIG. 8 is in their thermal capacitance. Theembodiment of the regulated amplifier system has a thermal capacitanceof 1600 joule per degree Celsius, while the regulated amplifier systemhas a thermal capacitance of 855 joule per degree Celsius.

The temperature line 54 of graph 34 has an initial temperature of around50° C. and rises to about 83° C. at the 1250 second time point beforedipping by around 2° C. at the 2000 second time point. At the 2000second time point, the line 54 then dips further from about 81° C. toaround 78° C. at the 2500 second time point prior to rising to about 80°C. at 3000 second time point. Then the graph line 54 falls toapproximately 63° C. at the 7000 second time point.

Thereafter, the graph line 54 rises from approximately 63° C. at the7000 second time point to about 82° C. at the 8000 second time pointbefore dipping by about 1° C. at the 9000 second time point. Then theline 54 falls from around 81° C. at the 9000 second time point to about80° C. at the 9100 second time point. After this, the graph line 54remains at approximately 80° C. from the 9100 second time point to the10,000 second time point.

The temperature graph line 54 of the further amplifier system, havingthe large mass heat sink, has a maximum temperature around the maximumtemperature limit T_(max) of for example 81° C. In comparison with thetemperature graph line 39 of FIG. 8 of the regulated amplifier system,the temperature graph line 54 has a slower rise and slower fall time.These are due to the large thermal capacitance of the further amplifiersystem.

FIG. 17 illustrates a temperature graph 35 of still a further regulatedamplifier system, which comprises a good thermal heat sink. Between thefurther regulated amplifier system, which comprises a good thermal heatsink and the regulated amplifier system 8 that generated the temperaturegraph line 39 of FIG. 8, the distinction is in the thermal resistanceR_(th). The further regulated amplifier system, which includes a goodthermal heat sink, has a thermal resistance R_(th) of 0.4° C. per wattdue to the good thermal heat sink while the regulated amplifier systemhas an R_(th) of 0.9° C. per watt.

The line 55 of temperature graph 35 starts with a temperature of around50° C. and rises to about 81° C. at the 2000 second time point. Then theline 55 decreases to approximately 70° C. at the 3000 second time point.After the 3000 second time point, the line 55 declines further fromaround 70° C. to about 51° C. at the 7000 second time point. From the7000 second time point, the line 55 rises from approximately 51° C. toroughly 79° C. at 9000 second time point. The line 55 then falls toapproximately 72° C. at the 10,000 second time point.

The maximum temperature of temperature line 55 is around theregulation-maximum temperature T_(max) of 81° C. The line 55 has atemperature peak of for example around 81° C. at the 2000 second timepoint and a temperature peak of about 79° C. at the 9000 second timepoint. Relative to temperature line 39 of the regulated amplifiersystem, the temperature line 55 shows a fast heat dissipation rate fromthe 2000 second time point to the 7000 second time point and from the9000 second time point to the 10,000 second time point. This is as oneexpects from a regulated amplifier system that has a good thermal heatsink.

FIG. 18 illustrates a temperature graph 36 of still yet anotherembodiment of a regulated amplifier system, which comprises a fancontrol unit. The regulated amplifier system that includes a fan controlunit of this embodiment has thermal parameters similar to that of theregulated amplifier system that generated the temperature graph line 39of FIG. 8. A primary distinction between the two amplifier systems isthat the former amplifier system has a thermal resistance R_(th) of 0.9°C. per watt when the fan is not operating and a thermal resistanceR_(th) of 0.5° C. per watt when the fan is operating. The fan isoperating when the amplifier system temperature T(n) exceeds a fan-starttemperature T_(fan) _(—) _(on) of 68° C.

The temperature graph 36 comprises a line 56 that starts at about 50° C.at 0 second time point and rises to approximately 81° C. at the 2000second time point. The line 56 then dips from about 81° C. at the 2000second time point to around 76° C. at the 3000 second time point. Thenline 56 declines further to around 64° C. at the 3420 second time point.After the 3420 second time point, the line 56 decreases at a slower rateto approximately 62° C. at the 7000 second time point.

The line 56 then increases from about 62° C. at the 7000 second timepoint to around 81° C. at the 9000 second time point. After the 9000second time point, the line 56 falls from approximately 81° C. by around1° C. at the 9200 second time point. The line 56 then remains around the80° C. level until the 10,000 second time point. The further regulatedamplifier system, which comprises a fan control unit, regulates thetemperature peak, in accordance the invention, to approximately 81° C.at the 2000 second time point as well as at the 9000 second time point.Line 56 displays a slower temperature decline rate from the 3420 secondtime point to the 7000 second time point than the temperature declinefrom the 3000 second time point to the 3420 second time point. This isbecause the thermal resistance of the amplifier system is higher whenthe fan is switched off from the 3420 second time point to the 7000second time point. The line 56 exhibits a fast temperature decline ratefrom the 2000 second time point to the 3000 second time point incomparison with the same period for temperature line 39 in FIG. 8. Thisis due to the lower thermal resistance of the further amplifier systemwhen the fan is operating. The fan is operating when the amplifiersystem temperature T(n) of the further amplifier system is above 68° C.

FIG. 19 illustrates a temperature graph 37 of still a another regulatedamplifier system, which comprises a poor thermal heat sink. Due to itspoor thermal heat sink, the amplifier system has a high thermalresistance R_(th) of 1.2° C. per watt. Other features of the amplifierare similar with the regulated amplifiers system that generated thetemperature graph line 39 of FIG. 8.

The line 57 of temperature graph 37 has a starting point of about 50° C.at 0 time point and rises to around 83° C. at 850 second time pointbefore falling slightly by about 1° C. at the 2000 second time point.The temperature then dips further from around 82° C. to approximately78° C. at the 2500 second time point before rising to about 80° C. atthe 3000 second time point. Then the line 57 decreases to around 68° C.at the 7000 second time point.

At the 7000 second time point, the temperature increases from around 68°C. to approximately 83° C. at the 7350 second time point prior todipping by about 1° C. at the 9000 second time point. From a temperaturein the region of 82° C. at the 9000 second time point, the temperaturegraph line 57 decreases by about 2° C. to around 80° C. at the 9050second time point and remains around this 80° C. point until the 10,000second time point.

There is a temperature peak of for example about 83° C. between the 0second time point and the 2000 second time point as well as between the7000 second time point and the 9000 seconds time. This is due to thetemperature control keeping the maximum temperature of the furtherregulated amplifier system to around T_(max) of for example 81° C. Theline 57 has a temperature of about 68° C. at the 7000 second time point.This temperature reading is about 8° C. higher than the same time pointon line 39 of FIG. 8 and is due to the poor thermal sink of the furtherregulated amplifier system.

Although examples of the invention have been described herein above indetail, it is desired to emphasis that this has been for the purpose ofillustrating the invention and should not be considered as necessarilylimitative of the invention, it being understood that many modificationsand variations can be made by those skilled in the art while stillpracticing the invention claims herein.

1. A method for regulating an amplifier system temperature T(n) of anamplifier system, where the amplifier system comprises a volume controlunit for inputting a listener's volume level setting V(n), a temperaturesensing unit for measuring the amplifier system temperature T(n), apower amplifier unit having an adjustable gain G(n), and a controllerconnected to the volume control unit, the temperature sensing unit, andthe power amplifier unit, the method comprising: receiving the volumelevel setting V(n) from the volume control; transmitting the amplifiersystem temperature T(n) from the temperature sensing unit to thecontroller; assessing whether the amplifier system temperature T(n) isgreater than a gain regulation temperature T_(reg) _(—) _(on); adjustingthe gain G(n) of the power amplifier unit to a target gain leveldetermined by the volume setting V(n) if the amplifier systemtemperature T(n) is below the gain regulation temperature T_(reg) _(—)_(on), or adjusting the gain G(n) of the power amplifier unit to atarget gain level between zero and the gain level determined by thevolume setting V(n) if the amplifier system temperature T(n) is abovethe gain regulation temperature T_(reg) _(—) _(on); and using historicalvalues of the amplifier system temperature T(n) for calculating thetarget gain G(n) of the power amplifier unit if the amplifier systemtemperature T(n) is above the gain regulation temperature T_(reg) _(—)_(on).
 2. A method for regulating an amplifier system temperature T(n)of an amplifier system, where the amplifier system comprises a volumecontrol unit for inputting a listener's volume level setting V(n), atemperature sensing unit for measuring the amplifier system temperatureT(n), a power amplifier unit having an adjustable gain G(n), and acontroller connected to the volume control unit, the temperature sensingunit, and the power amplifier unit, the method comprising: receiving thevolume level setting V(n) from the volume control; transmitting theamplifier system temperature T(n) from the temperature sensing unit tothe controller; assessing whether the amplifier system temperature T(n)is greater than a gain regulation temperature T_(reg) _(—) _(on);adjusting the gain G(n) of the power amplifier unit to a target gainlevel determined by the volume setting V(n) if the amplifier systemtemperature T(n) is below the gain regulation temperature T_(reg) _(—)_(on), or adjusting the gain G(n) of the power amplifier unit to atarget gain level between zero and the gain level determined by thevolume setting V(n) if the amplifier system temperature T(n) is abovethe gain regulation temperature T_(reg) _(—) _(on); and using a rate ofchange of the amplifier system temperature T(n) for calculating thetarget gain G(n) of the power amplifier unit.
 3. The method of claim 2,where the amplifier system temperature T(n) is assessed in timeintervals readings, the method further comprising the step of using thetwo most recent amplifier system temperature readings T(n) to computethe rate of change of the amplifier system temperature T(n).
 4. Themethod of claim 2, further comprising reading the values of theamplifier system temperature T(n) at regular intervals.
 5. The method ofclaim 4, further comprising computing the target gain G(n) of the poweramplifier unit based upon the following equation: $\begin{matrix}{{G(n)} = {{G\left( {n - 1} \right)} - {c_{d}\left\lbrack {{k_{n}{T(n)}} - {\sum\limits_{x = 1}^{x = a}{k_{n - x}{T\left( {n - x} \right)}}}} \right\rbrack}}} & (1)\end{matrix}$ where, the value of G(n) is in units of decibel, c_(d)comprises a constant value, k_(n) is a coefficient, a, n comprises ainteger value, 2≦a, k_(n−x)

k_(n−(x+1)) for 1≦x≦a, and$k_{n} = {\sum\limits_{x = 1}^{x = a}{k_{n - x}.}}$
 6. The method ofclaim 4, further comprising computing the target gain G(n) of the poweramplifier unit based upon the following equation:${G_{1}(n)} = {{G_{1}\left( {n - 1} \right)} - {c_{d}\left\lbrack {{k_{n}{T(n)}} - {\sum\limits_{x = 1}^{x = a}{k_{n - x}{T\left( {n - x} \right)}}}} \right\rbrack}}$where, the value of G₁(n) is in units of decibel, c_(d) comprises aconstant value k_(n) is a coefficient, a, n comprises a integer value,2≦a,${k_{n - x} \prec {k_{n - {({x + 1})}}\mspace{14mu}{for}\mspace{14mu} 1} \leq x \leq a},{{{and}\mspace{14mu} k_{n}} = {\sum\limits_{x = 1}^{x = a}k_{n - x}}}$G₂(n) = G₂(n − 1) + c_(i)[T_(m) − T(n)], where, the value G₂(n) is inunits of decibel, c_(i) comprises a constant value, and T_(m) is theupper temperature control limit of the amplifier system temperaturereading T(n), andG(n)=G ₁(n)+G ₂(n).
 7. The method of claim 6, further comprising thestep of setting the values of G₁(n) and G₂(n) to zero decibel when−G₁(n)<G₂(n).
 8. A method for regulating an amplifier system temperatureT(n) of an amplifier system, where the amplifier system comprises avolume control unit for inputting a listener's volume level settingV(n), a temperature sensing unit for measuring the amplifier systemtemperature T(n), a power amplifier unit having an adjustable gain G(n),and a controller connected to the volume control unit the temperaturesensing unit, and the power amplifier unit, the method comprising:receiving the volume level setting V(n) from the volume control;transmitting the amplifier system temperature T(n) from the temperaturesensing unit to the controller; assessing whether the amplifier systemtemperature T(n) is greater than a gain regulation temperature T_(reg)_(—) _(on); and adjusting the gain G(n) of the power amplifier unit to atarget gain level determined by the volume setting V(n) if the amplifiersystem temperature T(n) is below the gain regulation temperature T_(reg)_(—) _(on), or adjusting the gain G(n) of the power amplifier unit to atarget gain level between zero and the gain level determined by thevolume setting V(n) if the amplifier system temperature T(n) is abovethe gain regulation temperature T_(reg) _(—) _(on); and using more thanthe two most recent amplifier system temperature readings T(n) tocompute the rate of change of the amplifier system temperature T(n). 9.A method for regulating an amplifier system temperature T(n) of anamplifier system, where the amplifier system comprises a volume controlunit for inputting a listener's volume level setting V(n), a temperaturesensing unit for measuring the amplifier system temperature T(n), apower amplifier unit having an adjustable gain G(n), and a controllerconnected to the volume control unit, the temperature sensing unit, andthe power amplifier unit, the method comprising: receiving the volumelevel setting V(n) from the volume control; transmitting the amplifiersystem temperature T(n) from the temperature sensing unit to thecontroller; assessing whether the amplifier system temperature T(n) isgreater than a gain regulation temperature T_(reg) _(—) _(on); andadjusting the Gain G(n) of the power amplifier unit to a target gainlevel determined by the volume setting V(n) if the amplifier systemtemperature T(n) is below the gain regulation temperature T_(reg) _(—)_(on), or adjusting the gain G(n) of the power amplifier unit to atarget gain level between zero and the gain level determined by thevolume setting V(n) if the amplifier system temperature T(n) is abovethe gain regulation temperature T_(reg) _(—) _(on); and using thehistorical values of the gain G(n) of the power amplifier unit tocompute the target gain G(n) of the power amplifier unit.
 10. A methodof operating an amplifier system comprising an amplifier unit, atemperature sensor and a volume control unit, the method comprising:running the amplifier system with a desired volume level V(n); readingtemperature of the amplifier system T(n); verifying whether thetemperature of the amplifier system T(n) is above a gain regulationtemperature T_(reg) _(—) _(on); adjusting volume of the amplifier systemV(n) to a level between zero and a desired volume level when thetemperature of the amplifier system T(n) is above the gain regulationtemperature T_(reg) _(—) _(on); and using historical temperaturereadings of the amplifier system T(n) to choose the volume setting ofthe amplifier system V(n) when the temperature of the amplifier systemT(n) is above the gain regulation temperature T_(reg) _(—) _(on). 11.The method of claim 10, further comprising using the rate of change ofthe temperature of the amplifier system T(n) to choose the volumesetting of the amplifier system V(n).
 12. The method of claim 11,further comprising using the two most recent temperature readings T(n)of the amplifier system to compute the rate of change of the temperatureof the amplifier system T(n).
 13. The method of claim 12, furthercomprising using more than two of the most recent temperature readingsT(n) of the amplifier system to compute the rate of change of thetemperature of the amplifier system T(n).
 14. The method of claim 13,further comprising using the historical volume setting of the amplifiersystem V(n) to compute the volume setting of the amplifier system V(n).15. The method of claim 11, further comprising reading the temperatureof the amplifier system T(n) at regular intervals.
 16. The method ofclaim 15, further comprising: computing the volume setting of setting ofthe amplifier system unit based upon the following equation${G(n)} = {{G\left( {n - 1} \right)} - {c_{d}\left\lbrack {{k_{n}{T(n)}} - {\sum\limits_{x = 1}^{x = a}{k_{n - x}{T\left( {n - x} \right)}}}} \right\rbrack}}$where, the value of G(n) is in units of decibel, c_(d) comprises aconstant value, k_(n) is a coefficient, a, n comprises a integer value,2≦a,${k_{n - x} \prec {k_{n - {({x + 1})}}\mspace{14mu}{for}\mspace{14mu} 1} \leq x \leq a},{{{and}\mspace{14mu} k_{n}} = {\sum\limits_{x = 1}^{x = a}{k_{n - x}\mspace{14mu}{and}}}}$setting the volume setting of the amplifier system V(n) to the desiredvolume setting multiplied by the computed G(n).
 17. The method of claim15, further comprising computing the volume setting of setting of theamplifier system unit based upon the following equation:${G_{1}(n)} = {{G_{1}\left( {n - 1} \right)} - {c_{d}\left\lbrack {{k_{n}{T(n)}} - {\sum\limits_{x = 1}^{x = a}{k_{n - x}{T\left( {n - x} \right)}}}} \right\rbrack}}$where, the value of G₁(n) is in units of decibel, c_(d) comprises aconstant value, k_(n) is a coefficient, a, n comprises a integer value,2≦a,${k_{n - x} \prec {k_{n - {({x + 1})}}\mspace{14mu}{for}\mspace{14mu} 1} \leq x \leq a},{{{and}\mspace{14mu} k_{n}} = {\sum\limits_{x = 1}^{x = a}k_{n - x}}}$G₂(n) = G₂(n − 1) + c_(i)[T_(m) − T(n)] where, the value of G₂(n) is inunits of decibel, c_(i) comprises a constant value, and T_(m) is theupper temperature control limit of the amplifier system temperaturereading T(n),G(n)=G ₁(n)+G ₂(n),and setting the volume setting of the amplifiersystem V(n) to the desired volume setting multiplied by the computedG(n).
 18. The method of claim 17, further comprising setting the valuesof G₁(n) and G₂(n) to zero decibel when −G₁(n)<G₂(n).